No problem, let's work through this together. We're starting with 816996 and are subtracting 66075 from it.

Step 1: We'll start by subtracting the digit 5 and the borrow 0 from 6 in column 1 and get 1.
1 is the first digit of our result.

Step 2: We'll start by subtracting the digit 7 and the borrow 0 from 9 in column 2 and get 2.
2 is the next digit of our result.

Step 3: We'll start by subtracting the digit 0 and the borrow 0 from 9 in column 3 and get 9.
9 is the next digit of our result.

Step 4: We'll start by subtracting the digit 6 and the borrow 0 from 6 in column 4 and get 0.
0 is the next digit of our result.

Step 5: We'll start by subtracting the digit 6 and the borrow 0 from 1 in column 5 and get -5.
We add -5 to 10 and get 5 as the next digit of the result.

Step 6: We'll start by subtracting the digit 0 and the borrow 1 from 8 in column 6 and get 7.
7 is the next digit of our result.

So, 816996 - 66075 = 750921.